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The need for volunteer wheat control

With high wheat prices, producers should pay special attention to every management practice that can increase or protect yields. Controlling volunteer wheat is one such practice.

Volunteer wheat that emerges during the summer and is still present when planted wheat emerges creates numerous problems for the planted wheat crop, primarily:

* Wheat streak mosaic and associated viruses. Volunteer wheat is often infested with wheat curl mite, which serves as a vector for wheat streak mosaic and High Plains Virus. After planted wheat has emerged, the wheat curl mite populations on volunteer wheat can move onto the planted wheat.

* Hessian fly. Hessian fly pupae (or flaxseed) live through the summer on the stubble and crown of the previous season’s wheat crop. The pupae emerge as adults in late summer and early fall, and look for wheat to lay eggs on. If volunteer is close by, the Hessian fly adults will lay eggs on this wheat, thus maintaining their populations in that area and possibly infesting nearby planted wheat with the next generation.

* Barley yellow dwarf. As with the wheat curl mite, greenbugs and bird cherry-oat aphids can infest volunteer during the summer, and move onto planted wheat in the fall. These insects serve as a vector for barley yellow dwarf virus, and spread the disease to nearby fields.

* Russian wheat aphid. This aphid can also infest volunteer wheat during the summer and move onto planted wheat in the fall.

For these reasons, all volunteer wheat should be completely killed within a half-mile of wheat fields at least two weeks before planting. It is important to wait two weeks after the volunteer has died before planting wheat. This will allow for enough time for any insects or mites present on the volunteer wheat to leave the area or die before the new wheat emerges.

Where there is a heavy stand of volunteer, some producers may be tempted to leave it and either graze it out or harvest the grain next summer rather than kill it out and plant a new crop this fall. That’s not a good idea, however. The best option is to control the volunteer, then plant a new crop of wheat two weeks later rather than leave the volunteer for harvest. Producers could gain an extra 20-40 bushels or more of yield by planting a new crop of wheat instead of leaving the volunteer for harvest. Not only that, but they would also help their neighbors out by helping to reduce the chances of wheat streak mosaic, barley yellow dwarf, or Russian wheat aphid on their neighbor’s wheat as well.

What if the volunteer has not come up yet because of dry conditions? In this case, the volunteer may emerge at the same time the planted wheat emerges – after the next good rain event. Volunteer that does not emerge until the time planted wheat emerges, or even later, does not need to be controlled.

If the volunteer emerges shortly before wheat is planted, it’s probably still a good idea to get it controlled and wait two weeks after the volunteer wheat has died before planting – although late-emerging volunteer is less of a threat to harbor pests and diseases than earlier-emerging volunteer. Late-emerging volunteer provides a green bridge for a much shorter period of time.

Where volunteer is present before wheat planting, landowners and producers should do themselves and all their neighbors a favor, and control the volunteer two weeks before the wheat is planted.